Method of producing magnetic materials



Oct. 17, 1933.

Filed Sept. 10, 1930 l l I I l WKK A777.

Patented Oct. 17, 1933 PATENT oFFlcE METHOD 0F PRODUCING MAGNETIC MATERIALS Adolph F. Bandur, Berwyn, and Herbert M. E.

Heinicke, Elgin, Ill.,

assignors to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application September 10, 1930 Serial No. 480,850

8 Claims.

This invention relates to a method of producing magnetic materials, and more particularly to a method of improving the magnetic properties of cobalt magnet steel.

Objects of the invention are to provide an improved method whereby high retentivity and coercive forces of magnetic materials may be produced and the magnetic properties thereof may be materially improved.

In the general embodiment of the invention the alloy is heated slowly to a temperature of approximately 2100 F., retained at this temperature for a predetermined time to insure thorough heating, worked to reduce its cross-section, sheared into equal parts, reheated immediately, again reduced in cross-section sheared into equal parts, reheated immediately, and then worked to a final dimension. The outstanding feature resides in not allowing the material to cool during the working process.

The invention may be more fully understood from the following detailed description, reference being had to the accompanying drawing showing a curve illustrating a result of the method.

In carrying out this method, an ingot of cobalt steel containing from 9% to 36% of cobalt and weighing approximately 150 lbs. is inserted in a furnace, the temperature of which is below l600 F. and brought very slowly to a temperature of approximately 2l00 F., thus allowing the ingot to become heated slowly to the temperature of 2100 F. and retained at this temperature within the furnace for one hour to insure thorough heating. The ingot is then removed from the furnace and rolled or worked to reduce it to a billet of approximately two inches square in cross-section. The billet is immediately sheared into three equal parts, and the thus produced parts are recharged into the furnace where they are reheated to a temperature of approximately 2050 F. for a time suicient to insure the thorough heating thereof. As little time is spent in the rolling and the shearing of the material, the original temperature is substantially retained. The ingot is heated to a slightly higher degree of temperature than the billet or parts for the reason that the ingot, in its original state, is somewhat more difficult to roll. After heating the billet; that is, the three bars or parts, for the second time these bars are removed from the furnace and'reduced by further rolling to 7A; inch square rods, and each of the rods are sheared into three equal pieces, which are immediately'placed in' the furnace and reheated to a temperature of approximately 2050 F. After this reheating, the rods are removed from the furnace and rolled to 1/4 inch square rods, each of which is cut into 5 foot lengths and then cooled evenly in air to room temperature. The rods are then heated to approximately 1710" F. and quenched in oil.

During the steps of the process the material is heated slowly to a rolling temperature after which it is passed through a plurality of rolling 55 operations and reheated after each rolling operation, thus retaining the material in a softened condition until the last rolling operation is cornpleted, after which the material is allowed to cool to room temperature. The material may then be formed into the desired magnetic cores or parts, and heated to the hardening temperature of approximately 1710 F. and quenched in oil. By retaining the material in the softened condition during the entire rolling4 process, the 75 material is not only improved electrically, but is also improved mechanically. To illustrate the electrical improvement in the material, reference is made to the drawing which shows a curve derived from a test of a cobalt magnet 8o steel as a result of this process. In forming this curve the coercive force in Gilberts per Cm is plotted against the remanence in gausses per Cm. As indicated by the curve, the steels treated by this process have coercive forces of 220 to 300 Gilberts per Cm and remanences of 8,500 to 10,250 gausses per Cm2. The properties as indicated by the curve are materially improved over those obtained by previous methods of rolling.

The formation of surface imperfections such as scales and surface cracks are avoided in retaining the material in the softened condition. Furthermore, when the material is allowed to cool after each rolling operation, the surface of the material becomes very hard, making it more difficult to reheat uniformly, and under these conditions there are frequently portions of the material which remain in the hardened condition, not having been softened suitably by the reheating of the material, and thus causing mill marks upon the material when it is passed through another. rolling operation. Furthermore, the dropping of the material after each rolling operation and allowing the material to cool, forms marks upon the material which are avoided by the continuous rolling of the material without allowing the material to become cool.

By retaining the material in the softened condition, due to the reheating thereof after each rolling operation, the material is improved mechanically, and due to this improvement in the material, it is improved electrically. This results by preventing the formation of scales, surface cracks and mill marks on the material which necessitates reworking the material to place it in condition for a final product, and due to this improving of the material mechanically by eliminating these surface imperfections and the necessity of reworking of the material, the magnetic properties thereof are improved.

To aid in avoiding mill marks or other surface imperfections, tongs may be used which have asbestos lined jaws for handling the material during the process and by the use of these tongs the material is not cooled when handled.

What is claimed is:

1. A method of producing cobalt magnet steel, which consists in heating the magnet steel to a rolling temperature in the vicinity of 2100 F., reducing the cross-sectional area of the magnet steel, reheating the magnet steel before it cools substantially to retain the rolling temperature, again reducing the cross-sectional area thereof, reheating the steel to a temperature of approximately 1710 F., and quenching the steel.

2. A method of manufacturing cobalt magnet steel, which consists in heating the steel to a rolling temperature in the vicinity of 2100 F., subjecting the steel to a plurality of reducing operations While maintaining the rolling temperature, and quenching the steel.

3. A method of manufacturing cobalt magnet steel, which consists in heating the steel slowly to a temperature of approximately 2100 F. to insure thorough heating, reducing the cross-sectional area of the steel, reheating the steel to a similar temperature before it cool's substantially, and again reducing the cross-sectional area of the steel.

4. A method of manufacturing cobalt magnet steel, Which consists in heating the steel to a temperature of approximately 2100 F., reducing the cross-sectional area of the steel, shearing the steel into predetermined lengths, reheating the steel to a temperature of approximately 2100 F. before it cools substantially, and again reducing the cross-sectional area of the steel.

5. A method of manufacturing cobalt magnet steel, which consists in heating the steel to a temperature of approximately 2100 F., reducing the cross-sectional area of the steel, shearing the steel into predetermined lengths, reheating the steel to a temperature of approximately 2100 F. before it cools substantially, again reducing the cross-sectional area .of the steel, shearing the parts into predetermined lengths, reheating these sheared parts to a temperature of approximately 2050 F., and reducing the cross-sectional area of each of Vthese parts.

6. A method of manufacturing cobalt magnet steel, which consists in heating the steel to a temperature of approximately 2100 F., reducing the cross-sectional area of the steel, shearing the steel into predetermined lengths, reheating the steel to a temperature of approximately 2100 F. before it cools substantially, again reducing the cross-sectional area of the steel, shearing the parts into predetermined lengths, reheating these sheared parts to a temperature of approximately 2050 F., reducing the crosssectional area of each of these parts to nal size, cooling to room temperature, reheating the parts to 1710 F., and quenching the parts in oil.

7. A method of manufacturing cobalt magnet steel, which consists in heating the steel slowly to a temperature of approximately 2100 F., reducing the cross-sectional area of the steel, shearing the steel into predetermined lengths, reheating the steel to a temperature of approximately 2050 F. before it cools substantially, again reducing the cross-sectional area of the steel to nal size, and cooling to room temperature.

8. A method of producing cobalt magnet steel, which consists in heating steel to a temperature of approximately 2100 F., reducing the crosssectional area of the steel, reheating the steel to substantially the same temperature before it has had time to cool, again reducing the crosssectional area thereof, and repeating the reheating and reducing steps untilthe steel has been reduced to a desired size and contains electrical properties for use as a magnet steel.

ADOLPH F. BANDUR. HERBERT M. E. HEINICKE. 

